In comparison with electric motors, internal combustion engines used in automobiles or the like have a feature that the torque increases according as the speed of rotation goes up, with a small torque at a low speed of rotation. In automatic variable speed vehicles mounted with such internal combustion engines, use is made of, e.g., a torque converter for increasing the torque to make up for a lack of torque at a low speed rotation. Due to the torque converter which effects transmission of power with a slip, however, the automatic variable speed vehicles are inferior in accelerating ability and fuel efficiency to manual variable speed vehicles incorporating a pressure connection type clutch, with a slight shock at a gear change remaining unsolved. Recent development is therefore directed toward variable speed change gears capable of freely varying the change gear ratios and ensuring traveling within a range in which is generated maximum output or maximum torque of the engine. This will achieve improvement in accelerating ability and fuel efficiency, as well as elimination of shocks at a gear change, which are problems involved in the automatic variable speed vehicles. Currently known as the most typical variable speed change gear is one employing a metallic belt and a pair of pulleys, in which type the groove widths of the pulleys are continuously varied so as to vary the radii of the belt passing around the pulleys to thereby perform speed variation.
In the variable speed change gear serving to transmit the power with the aid of frictional force generated between the belt and the pair of pulleys as described above, inconveniently, a larger-sized apparatus is required for transmitting a higher level of power due to a reduction in efficiency of power transmission. This resulted in inability of application to widespread fields, including limitation to the small-sized vehicles if mounted on the motor vehicles.
The present invention was conceived in view of the above problems. It is therefore the object thereof to provide a variable speed change gear ensuring an effective transmission of power.